Process of forming an impregnated cathode

Abstract

A cathode and a process of manufacturing the same are disclosed, the cathode comprising; a molybdenum cup having a convex portion, free barium atoms produced through reactions with an impregnation compound, a porous metal layer sealingly welded to the top of the cup, and a heating member having an uppermost head portion inserted into the lower space of the convex portion of the cup. According to the cathode of the present invention, the disadvantages of the conventional cathodes such as the speedy evaporation of barium during the initial stage, and the degrading of the performance and the shortening of the life expectancy due to the reaction byproducts produced in the porous metal layer can be overcome, while a quick start-up characteristics can also be obtained owing to the speedy diffusion of the barium.

What is claimed is: 
     
       1. A method of manufacturing a cathode for an electron tube, comprising the steps of: filling a reducing agent into a metal cup having an open top such that 10 to 100% of the volume of said cup is filled with said reducing agent;   sealing said cup at the top with a layer of porous metal to form thereby an electrode;   melting an impregnation compound;   passing the impregnation compound through pores of said porous metal layer into said cup to cause thereby said impregnation compound and reducing agent to react with each other; and   injecting an inert gas through the pores of said porous metal layer to remove compound in said pores.   
     
     
       2. The method according to claim 1, wherein said reduction agent contains 80-100 wt% tungsten powder having a purity of over 99%, 0-20 wt% silicon powder, and 0-20 wt% magnesium powder. 
     
     
       3. The method according to claim 1, wherein said porous metal layer is made up of tungsten or tungsten containing at least one of the following elements: nickel, steel and cobalt, in the amount of 0.05-10 wt%. 
     
     
       4. A method according to claim 1, wherein said cup is made of molybdenum. 
     
     
       5. A method according to claim 1, wherein the porosity of said metal layer is 10 to 40%. 
     
     
       6. A method according to claim 1, comprising melting said impregnation compound and passing same through the pores in said porous metal layer in an impregnation tank within a vaccum furnace.